To address the strength fluctuation observed in Ti microalloyed steel, the effects of final rolling temperature, coiling temperature, and Ti content on the microstructure, secondary phase precipitation behavior, and grain size were investigated through simulation experiments. Various characterization techniques were employed to elucidate the underlying causes of the strength variation, and key control strategies were proposed. The results indicate that the strength fluctuation is primarily influenced by the presence of nano-sized TiC precipitates. The precipitation behavior of TiC can be effectively controlled by adjusting the content of non-metallic elements as well as the final rolling and coiling temperatures. Higher final rolling temperatures combined with appropriate coiling temperatures promote increased TiC precipitation; however, excessively high temperatures may result in grain coarsening and inhomogeneous precipitate distribution. The optimal processing parameters were determined to be a final rolling temperature of 860 °C and a coiling temperature of 600 °C.

This paper proposes a source-level electromagnetic interference suppression strategy for high-voltage inverters that uses a series-connected IGBT topology and discrete staircase voltage shaping. From an information-theoretic perspective, the staircase shaping transforms chaotic wideband switching noise into a deterministic harmonic structure, thereby reducing the spectral entropy of the EMI source. This information optimization is achieved using a CPLD-based sequential gate drive circuit, which eliminates the need for complex active gate profiling algorithms. Experimental results obtained using a 1140 V explosion-proof motor drive platform demonstrate harmonic attenuation of 4–16 dB μV within a 2 MHz band. Importantly, this targeted entropy reduction occurs alongside a 68.7% reduction in active-region switching losses, suggesting a concurrent decrease in local thermodynamic entropy production during switching transients. Increasing spectral determinism and relaxing requirements for subsequent physical filters effectively lower the conditional entropy of the overall electromagnetic environment. Leveraging the structural flexibility of series IGBTs, this method provides a practical, low-complexity solution and establishes a novel framework between power electronics and information theory for electromagnetic compatibility.

Inverters generate significant EMI due to their rapid switching operations. This paper proposes an EMI suppression scheme at the source level based on a series IGBT topology and voltage shaping. By reshaping the output voltage waveform, the scheme periodically suppresses the EMI source. Furthermore, staircase voltage shaping is implemented using a CPLD-based sequential gate drive circuit, eliminating the need for complex modifications to existing gate drive circuits. Experimental results on an 1140 V explosion-proof induction motor drive platform demonstrate that this method achieves harmonic attenuation of 4-20 dBμV within a 2 MHz bandwidth period. Compared to traditional two-level inverters, total switching losses are reduced by around 70%. Periodic EMI suppression also simplifies the design complexity of other EMI mitigation methods within the system. Its periodic nature also enhances design predictability. Moreover, this approach leverages the flexibility and scalability of the series IGBT structure to provide a practical solution for high-voltage inverter systems. It enables source-level EMI suppression without significantly increasing system complexity or cost.